Despite his draft status, and spending time on Chicago's 40-man roster, he never played in Major League Baseball (MLB).

The Tampa Bay Rays selected Gillaspie in the first round, 20th overall, of the 2014 Major League Baseball Draft.

[5] He signed on June 10[6] and was assigned to the Hudson Valley Renegades, where he posted a .262 batting average with seven home runs and 42 RBIs.

In 2016, Gillaspie spent time with both the Montgomery Biscuits and the Durham Bulls, posting a combined .284 batting average with 18 home runs, 64 RBIs and an .866 OPS between the two clubs.

On January 20, 2023, Gillaspie was claimed off waivers by the Sioux City Explorers of the American Association of Professional Baseball.

[14] Gillaspie's brother, Conor, also played college baseball at Wichita State and retired from the MLB in August 2017.